My thinking was more on the almost religious bond between a samurai and his daimyo/lord. To be disloyal to one's lord was a horrible offense to his honor and the samurai's. Let's not forget ritual seppuku. But, okay, whatever floats your boat.
By the way, maybe we should add some kind of honor statistic? Players can gain or lose honor through victory or defeat (respectively) in battle, duels, etc. Just a thought.